1. Field of the Invention
The present invention relates to a thermal treatment apparatus and method which supplies heat and atmospheric gas to a thermal treatment chamber as a function of a measured temperature in the thermal treatment chamber.
2. Description of the Related Art
FIG. 4 is a block diagram showing a conventional thermal treatment apparatus. As shown there, the thermal treatment apparatus 50 comprises a heating system 51 and a gas supplying system 52. A recorder 53 records a temperature in a thermal treatment chamber 54 and also records the amounts of gas supplied to the thermal treatment chamber.
The heating system 51 includes heaters 55 for heating the thermal treatment chamber 54 and thermocouples 56 for measuring the temperature of the thermal treatment chamber 54. A plurality of temperature controllers 57 control the heating conditions of the heaters 55 through a respective plurality of thyristors 58 in accordance with the temperature in the thermal treatment chamber 54 as measured by the thermocouples 56.
The gas supplying system 52 includes gas flow rate controllers 60 for controlling amounts of atmospheric gas delivered to the thermal treatment chamber 54 from an atmospheric gas supply section (not shown) through mass flow controllers 59.
The thermal treatment apparatus 50 controls a heating condition and a gas supply condition in the thermal treatment chamber 54 as follows. The temperature controllers 57 control the heating condition in a time sequence based on temperature information received from the thermocouples 56, while the mass flow rate controllers 59 control the gas supply in a time sequence based on signals received from the gas flow rate controllers 60. More specifically, when it is detected that the thermal treatment chamber 54 reaches a predetermined temperature on the basis of temperature information received from the thermocouples 56, the temperature controllers 57 and the gas flow rate controllers 60 supply heat and gas corresponding to pre-set profiles. These profiles specify the manner in which the thermal treatment chamber 54 is controlled as a function of the sensed temperature of the thermal treatment chamber 54. Time measuring means (not shown) in the controllers 57 and 60 then measure fluctuation points in the profiles (that is, points in time where gradients of the profiles change), so that heat control and gas supply control corresponding to the profiles are performed on the basis of the results of the time measurement.
The conventional thermal treatment apparatus 50 constructed as described above encounters a number of problems. As described above, the heating system 51 and the gas supplying system 52 control the heating and gas supplying conditions following the profiles based on the time measuring means included in each of the controllers 57 and 60. However, the heating system 51 and the gas supplying system 52 control the profiles based on time measured by different time measuring means. It is therefore difficult to make the timing of the heating profile fluctuation point coincide with that of the gas supply profile fluctuation point. Particularly, in profiles that have a long time interval between profile fluctuation points, it is difficult to make the timings coincide with each other. For this reason, the heating system 51 and the gas supplying system 52 cannot be controlled in relation to each other with high accuracy, so heat treatment with high accuracy can not be performed.
In addition, the heating and the gas supply profiles are inputted to the temperature controllers 57 and the gas flow rate controllers 60, respectively, in accordance with the object to be heat-treated. At this time, the profiles should be inputted in relation to each other such that the profile fluctuation points coincide with each other. However, these profiles are inputted to different controllers 57 and 60, so that it is very difficult to input the profiles in relation to each other. Particularly, in recent years, the thermal transfer chamber 54 has been divided into a plurality zones to control heating, and to supply a plurality of atmospheric gases (e.g., referring to FIG. 4, the heating is controlled in three zones, and three types of atmospheric gas are supplied). This compounds the complexity and difficulty associated with inputting the profiles for controlling the heating and gas supply in relation to each other, making inputting errors a likely occurrence.
Further, the more complicated control becomes, the more the number of controllers 57 and 60 increases, thereby causing an increase in the cost of the apparatus.